MRSA Strikes New Population: Young Children

By Pat McGinley, FNP, MSN

Summary-Researchers found a 39% increase in the incidence of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) when they completed a retrospective review of children's medical records at a university-based teaching hospital. Penicillin is the drug of choice. However, 90% of staphylococci are resistant to penicillin, and treatment should include a penicillinase-resistant antibiotic. Clinicians should consider MRSA if patients fail to respond to antibiotic therapy within 48-72 hours. Clinicians must educate patients and parents to the dangers of developing drug resistance by using antibiotics unnecessarily, i.e. for viral illnesses. Strict hand washing and meticulous cleansing of equipment is critical to avoid spreading the bacteria.

An alarming increase in the incidence of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) is being reported among children. In the Feb. 25, 1998, Journal of the American Medical Association, researcher Betsy Herold, MD, and colleagues were surprised to note community-acquired MRSA infections in children without risk factors who were admitted to a university-based teaching hospital. That observation prompted a retrospective review of the medical records of children diagnosed with community-acquired MRSA and showed an increase in prevalence, especially among toddlers.1

Staphylococcus aureus, a gram positive micrococci considered normal human flora on human skin and mucous membranes, is found in the anterior nares and moist body areas in about 30% of asymptomatic people. Transmission occurs via hands, nasal discharge, person-to-person contact, and rarely through air.2

S. aureus causes various pathogenic conditions from superficial infections, such as boils, carbuncles, and abscesses, to toxic reactions such as toxic shock and Stevens Johnson syndrome.

The drug of choice to eradicate S. aureus is penicillin and its derivatives, including methicillin. Penicillin inhibits bacterial growth by interfering with bacterial cell wall synthesis. MRSA inactivates penicillin through the enzyme, beta lactamase.

Alice Prince, MD, at the Columbia University College of Physicians and Surgeons and Columbia Presbyterian Medical Center, writes that 90% of staphylococci are resistant to penicillin. Therapy should include a penicillinase-resistant antibiotic such as methicillin, oxacillin, nafcillin, or first-generation cephalosporins (cephalothin, cefazolin, and clindamycin), according to Prince.1

Risk Factors for MRSA

MRSA emerged in the 1950s, soon after the introduction of methicillin,3 and is now a worldwide problem. MRSA has been an infection control problem within U.S. hospitals since the 1970s.4,5 Patients with risk factors such as intravenous drug abuse, extensive burns, open wounds, chronic illnesses, and protracted hospital admissions are most susceptible to these bacteria. Failure to eradicate the bacteria leads to bacteremia, septic shock, and death in 90% of cases.6

The study by Herold et al1 shows isolation of MRSA is no longer limited to patients with predisposing factors or those at risk for nosocomial infection. Even worse, the incidence of multidrug-resistant bacteria threatens inpatient and outpatient management of common acute and chronic infections.

Herold and colleagues report a trend for MRSA to strike pediatric populations without risk factors. In the JAMA article, they outline research using retrospective analysis of community-acquired MRSA infections among children admitted to the University of Chicago Hospitals.1

On retrospective review of inpatient records, the researchers found an increase in the incidence of MRSA from 10 per 100,000 admissions during 1988-1990 to 259 per 100,000 admissions during 1993-1995 in the pediatric population. They compared the cases of MRSA in terms of the following:

    · age;

    · race;

    · sex;

    · date of admission;

    · site of culture resulting in growth of S. aureus;

    · date of specimen collection;

    · prior antibiotic use before hospitalization;

    · previous admission to other health care facilities;

    · underlying medical conditions as well as pertinent family history.

They found no significant differences between the study groups.

The authors defined and categorized each case into community-acquired or nosocomially-acquired infection. Community-acquired MRSA was defined as an infection isolated within 72 hours of admission to the hospital. Nosocomially-acquired infection was defined as infection resulting after 72 hours of admission.

Results indicated an increase in community-acquired MRSA from 25% of the 1988-1990 cases to 64% during the 1993-1995 time frame. Of the latter, only 30% had risk factors for contracting MRSA, compared with 88% of cases in the 1988-90 group.

In community-acquired MRSA without risk factors, the only significant variable between the time periods was the age distribution. Toddlers showed a higher incidence in the 1993-1995 study group. The most common diagnosis associated with community-acquired MRSA without risk factors was cellulitis or abscess, whereas the most common diagnosis of nosocomial-acquired MRSA without risk factors was bacteremia.

The authors speculate that the rising incidence of community-acquired MRSA, especially in the toddler populations, may be due to increased day care utilization and increased rates of transmission.

Most importantly, the MRSA cases without risk factors were not multi-drug resistant. Community-acquired MRSA did respond to other non-beta-lactam antibiotics. Bactrim DS (Roche Laboratories, Nutley, NJ) and clindamycin are the drugs of choice today. Vancomycin still remains in the bank for treatment of other multidrug- resistant bacterial illnesses.

Implications for Practice

The study has several important implications for the advanced practice nurse. We must be cognizant of the prevalence of drug-resistant bacteria in our own communities. Consider MRSA in the differential diagnosis for patients who do not respond to antibiotic therapy within 48-72 hours. Inform the patient or parents that you expect improvement within that time frame and must be notified if none is shown.

All health care practitioners must prescribe antibiotics judiciously. We must educate patients and parents regarding drug-resistant bacterial illnesses and explain why antibiotics are not always the answer. Citing research-based evidence of bacterial illnesses that no longer respond to the usual antibiotics, especially in children, gives credibility to the health practitioner's message.

Most importantly, we must resist the temptation to prescribe antibiotics for illnesses that are often viral in nature despite parents' or patients' insistence on a prescription.

The emergence of MRSA and other bacteria as well as new viral illnesses demands education about effective hand washing to limit transmission of disease. Conscientious attention by all inpatient and outpatient health care providers, patients, parents, and caretakers to strict hand washing techniques and meticulous cleansing of equipment, especially stethoscopes, is essential to avoid spreading the bacteria. (See story describing the University of Michigan's study on stethoscopes and harmful bacteria, below.)

References

    1. Herold B, Immergluck L, Maranan M, et al. Community-acquired methicillin-resistant Staphylococcus aureus in children with no identified predisposing risk. JAMA 1998; 279 (8):593-598.

    2. Prince A. Infectious diseases. In: Nelson Essentials of Pediatrics. 2nd ed.Philadelphia: W.B. Saunders; 1994, pp. 348-351.

    3. Jevons MP. "Celbenin"-resistant staphylococci. British Medical Journal 1961; 1:124-5.

    4. McCance K, Huether S. Pathophysiology: The Biologic Basis for Disease in Adults and Children. Third Edition. St. Louis: C.V. Mosby Co.; 1998, p. 254.

    5. Musser J. Molecular population genetic analysis of emerged bacterial pathogens: Selected insights. Emerg Infect Dis 1996; 2(1:1-22 via Internet access and download: http://www.cdc.gov.

    6. Behrman R, Kliegman R, Arvin A. Nelson Textbook of Pediatrics. 15th Edition. Philadelphia: W.B. Saunders; 1996, p. 748.